In the communication between mobile stations, in receiving television broadcasts or radio wave on an ordinary vehicle, or in the recognition of its own position on a vechile, marine vessel or aircraft (hereinafter collectively referred to as vehicle), an antenna with an associated antenna attitude control system is mounted on such vehicle in order to receive a radio wave from a land-based (including maritime) fixed station or geostationary satellite, or to transmit a radio wave toward such land-based fixed station or geostationary satellite to receive a reflection therefrom. Examples of such technique are disclosed in Japanese Laid-Open Patent Application Nos. 140,302/1980 and 89,101/1981.
The former disclosure relates to the antenna attitude control of self-tracking type. Specifically, as a marine vessel moves, the amount of a shift in the position of the marine vessel corresponding to such movement is calculated on the basis of the direction in which and the distance through which the vessel has moved. An offset in the position of the antenna relative to the fixed base station which corresponds to such shift is calculated from the amount of shift in order to alter the position of the antenna relative to the fixed base station. The amount of shift is accumulatively added to the position which the vessel assumed before the movement to determine the current position of the vessel. This technique has both the mobile communication (relay of a television broadcast) and the recognition of the position of a mobile body for its objects.
The latter disclosure relates to the antenna attitude control of so-called programmed tracking type. Specifically, for a vehicle which travels along a given route, the positions of the antenna at various points along the route which provide an optimum reception relative to a particular fixed station are previously stored, and a distance from an origin which has been travelled by the vehicle is used to an access a memory to read a corresponding position of the antenna, thus altering the position of the antenna.
Problems experienced with the antenna attitude control of either self-tracking or programmed tracking type mentioned above are how to enable a correction to be effected in the antenna position so as to track a rapid movement of the mobile body and how to reduce an error in the position detected, in particular, an accumulated error inasmuch as the location of the movable body represents a principal parameter when establishing the position of the antenna. Depending on the manner of movement of the mobile body, the antenna may face away from a target station, causing a reduction in the reception level or inability of reception. Such tendency is pronounced for a rapid removing mobile body of a small size. For example, considering an automobile, the position of the vehicle or more exactly the position of the antenna may change in various manners depending on the road conditions or the running conditions even though the automobile runs on the same road. Where a high directivity antenna is used, the reception may be interrupted during the running depending on the running condition even though the line of sight is maintained.